Business process (BP) stakeholders want to enjoy the benefits of the cloud, but they are also reluctant to expose their BP models which express the know-how of their companies. To prevent such a know-how exposure, this paper proposes a design-time approach for transforming a BP model into BP fragments so that these BP fragments externalized in a multi-cloud context do not allow a cloud resource provider to understand a critical fragment of the company. While existing contributions on this topic remain at the level of principles, we propose an algorithm supporting automatically such a BP model transformation.